In existing RAID storage systems, multiple storage devices can be used to implement a logical volume of data. When the data for the volume is kept on multiple storage devices, the data can be accessed more quickly because the throughput of each individual storage device can be combined. Furthermore, when the data is stored on multiple storage devices, redundancy information can be maintained so that the data will be preserved even if a storage device fails. In RAID storage systems, sets of disks known as “spans” may each implement an independent RAID configuration. However, when multiple spans are used to implement a logical volume, each span uses the same RAID configuration, the same number of drives, and the same drive capacity.